Methods Of Metal Extraction Using Oximes

ABSTRACT

Provided are methods method of recovering metal from an aqueous solution, the method comprising contacting an aqueous solution containing at least two metals selected from molybdenum, cobalt, nickel, zinc and iron with an organic solvent and an oxime-containing reagent composition at a predetermined pH, the predetermined pH selected to provide a high first metal extraction and a low second metal extraction; and separating the first metal from the solution.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/401,939, filed Feb. 22, 2012, which claims priority to U.S.Provisional Patent application No. 61/446,878, filed on Feb. 25, 2011,the contents of both of which are incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates generally to the field of extractivemetallurgy. In particular, the present invention relates to metalsolvent extraction methods and reagents.

BACKGROUND

Copper and its metal alloys have been used for thousands of years. Theimportance of copper, as well as a variety of other metals, has led to acontinuing search for more efficient and productive procurement methods.One method of copper extraction is a process of leaching, coupledtogether with solvent extraction, and finally copper production byelectrowinning. Leaching is typically carried out by stacking the ore inpiles on a prepared pad or by stacking it in a small canyon. A solutionof sulfuric acid is then applied, and as the acid solution is trickleddown through the heap, copper is dissolved from the rock. The resultantcopper-bearing solution (pregnant leach solution or PLS) is collected,and then transferred to the solvent extraction plant, where it iscontacted by vigorous mixing with an organic solution comprising anextractant dissolved in a kerosene-like hydrocarbon diluent. In thisextraction, the copper (as cupric ion) is transferred to the organicphase, where it forms a chelate-type complex with the extractant. Aftercontact, the mixture of aqueous and organic is allowed to separate. Thecopper-depleted aqueous solution (raffinate) exits the solventextraction plant, and the organic is transferred to stripping, where itis contacted with a strong acid solution. In stripping, the cupric ionis transferred to the aqueous phase and protons are transferred to theorganic. The now copper-depleted organic is returned to extraction forre-use. The copper-rich aqueous strip solution (pregnant or richelectrolyte) is transferred to electrowinning. In electrowinning, copperis plated as metal from solution at the cathode, and water is brokendown at the anode to form oxygen and protons as acid. Depending on theclimatic conditions at the site, the size of the ore heap or dump, andthe irrigation rate, the temperature of the PLS entering the plant couldrange from about 10° C. to about 30° C. As a result, temperatures inextraction typically range from about 20 to 25° C., and temperatures instripping may range from about 30 to 35° C. The temperature in theelectrowinning cells is typically about 45° C., incorporated herein byreference. This acid leach process may also be used for other metals.Additionally, leaching with ammonia may be carried out analogously.Combinations of ammonia with an ammonium salt, such as ammoniumcarbonate or ammonium sulfate, have been used on a commercial scale toleach copper metal (recycling applications), copper oxide ores andcopper sulfide ores. Ammonia leaching can be applied other metals suchas nickel and zinc as well.

Reagents useful in such processes should generally possess certainqualities. Examples of important features are the rates of reaction,phase separation and reagent stability. A detailed discussion of theuseful characteristics in a liquid ion exchange reagent is available inSwanson, “Liquid Ion Exchange: Organic Molecules for Hydrometallurgy”presented at the International Solvent Exchange Conference September1977.

Several extractant reagents have been used, including some phenolicoxime extractants. Among those used are 5-nonylsalicylaldoxime,5-nonyl-2-hydroxyacetophenone oxime and 5-dodecylsalicylaldoxime.However under certain conditions of use, the current reagents are notideal and have had issues not yet fully addressed. For example, thesealdoximes bind copper very tightly, and only a small part of the coppercan be recovered in stripping under the commercially typical conditionsof acid and copper content in the lean electrolyte that is used as stripmedia. To maximize stripping, one typically adds a thermodynamicmodifier to the extractant. Alternatively, extractants can be formulatedthat have different relative extractant strengths, which stripsignificantly better than the standard aldoximes by themselves. Blendsof aldoximes and ketoximes have been used, and demonstrate thatketoximes act as an extractant, as well as a thermodynamic modifier.However, the copper content on the stripped organic is lower than onewould expect based on consideration of the stripping behavior of theindividual oximes.

Another general problem is extractant loss (also known as degradation)via chemical hydrolysis to the corresponding ketone or aldehyde. Theconcentration of the hydrolysis products in the organic phase increasesuntil the rate of formation equals the rate of loss in entrainment. Therate at which hydrolysis occurs is dependent on the acid concentrationand the temperature of the system. Current reagents may not workproperly due to hydrolysis. One trend in the industry is towards thetreatment of primary copper sulfide concentrates by hydrometallurgicalroutes rather than smelting. These processes result in the production ofleach solutions which are very warm. Solutions fed to the copper solventextraction process will range in temperatures from about 35° C. to 50°C., or higher. Higher temperatures also occur when the oxide ores areextremely rich, such as the ores from the Democratic Republic of theCongo. They are typically vat or agitation leached with sulfuric acid.The leaching reactions are quite exothermic, resulting in PLS forextraction that are higher in temperature than typical heap or dumpleach operations. The higher temperature results in a significantlyhigher rate of hydrolysis of the oxime extractants. This leads tobuildup of the hydrolysis products in the circuit organics to very highlevels relative to that observed in typical head and dump leachoperations. Due to the higher rate of degradation, the level ofdegradation products can approach levels as high as 100% of the oximeconcentration in the circuit organics. This results in a significantincrease in the density and viscosity of the organic phase, which inturn is reflected in slower phase disengagement and higher entrainments.

Another problem with current technology is with copper selectivity overiron. Copper/iron selectivity is very important for some solventextraction/electrowinning systems. Iron that is transferred to theelectrowinning system has a negative effect on the processing of copperin the electrolyte. As the concentration of ferric ions increases, thereis a substantial drop in current efficiency. In addition to the costincurred by the drop in current efficiency, there is the additional costof bleeding the system to control the iron concentration. Bleedingelectrolyte results in the reduction of cobalt concentration (inaddition to other additives) which is added to protect lead anodes, andthis can be a large expense in an electrowinning plant.

Current reagent technology could also be improved when nitrate ispresent in the PLS or strip solution. Nitrate in the PLS or stripsolution can lead to attack on the phenolic oximes resulting innitration of the ring to form the corresponding 3-nitro aldoximes orketoxime. The nitro oximes are extremely strong copper chelators. Theycannot be stripped under typical plant conditions resulting in loss ofnet transfer. Such problems are discussed in the Virnig, et al.,“Effects of nitrate on copper SX circuits: A case study” in ProceedingsCopper 2003-Cobre 2003, Vol VI-Hydrometallurgy of Copper (Book1), editedby P. A. Riveros, D. Dixon, D. B. Dreisinger, J. Menacho; CanadianInstitute of Mining, Metallurgy and Petroleum; Montreal, Quebec, Canada;2003, pp 795-810. There have been attempts to deal with this nitrationissue. For example, it has been proposed to add lower molecular weightphenol to the extractant formulation as a sacrificial lamb. The phenolis more readily nitrated than is the oxime, and so long as there is anyphenol present, the oxime is protected. However, as soon as the phenolis consumed, then nitration of the oxime will occur.

Yet another problem relates to currently used oximes for extraction ofcopper and nickel from ammoniacal solutions. In applications involvingextraction of nickel or copper from ammonia, one typically finds thatdegradation of the organic by hydrolysis of the oxime is an issue.During such extraction, the resultant complex carries with it somechemically bound ammonia, which is undesirable. The ammonia istransferred to stripping where it consumes acid to form thecorresponding ammonium salt which builds up overtime in the circulatingelectrolyte and can lead to the formation of insoluble salts such asnickel ammonium sulfate which can cause plugging of lines, etc. There isthus a need for reagents and/or methods that address one or more ofthese problems.

SUMMARY

One aspect of the invention relates to a method of extracting a metalfrom a nitrate-containing aqueous solution, the method comprisingcontacting a nitrate-containing aqueous solution containing dissolvedmetal values with an organic phase comprising a water immiscible solventand a reagent composition comprising an oxime having a structurerepresented by:

wherein R¹ is hydrogen or CH₃, R³ is a C8-12 alkyl group, R² and R⁴ arehydrogen, R⁵ is a methyl group, to extract at least a portion of themetal values into the organic phase to provide a metal-pregnant organicphase and a metal-barren aqueous phase; separating the resultantmetal-pregnant organic phase from the metal-barren aqueous phase; andrecovering metal values from the metal-pregnant organic phase.

In one or more embodiments of this aspect, the oxime is a ketoximehaving a structure represented by:

In one or more further embodiments, the organic phrase further comprisesan aldoxime having a structure represented by:

According to one or more embodiments, the ketoxime and aldoxime arepresent in a molar ratio of ketoxime to aldoxime ranging from about85:15 to about 25:75.

In one or more embodiments of this aspect, the oxime is an aldoximehaving a structure represented by:

In one or more further embodiments, the organic phrase further comprisesan aldoxime having a structure represented by:

According to one or more embodiments, the ketoxime and aldoxime arepresent in a molar ratio of ketoxime to aldoxime ranging from about85:15 to about 25:75.

According to one or more embodiments, the metal is selected from thegroup consisting of copper, molybdenum, uranium, rare earth metals andcombinations thereof. In some embodiments, the metal is copper.

The nitrate-containing aqueous solution may have various concentrationsof nitrate, chloride and pH. In one or more embodiments, thenitrate-containing aqueous solution has a concentration of nitrate thatranges from about 3 grams per liter to about 30 grams per liter. In someembodiments, the nitrate-containing aqueous solution has chloride in aconcentration ranging from about 1 gram per liter to about 30 grams perliter. In some embodiments, the pH of the nitrate-containing aqueoussolution ranges from about 0.6 to about 2.0.

Another aspect of the invention relates to a method of recovering metalfrom an aqueous solution, the method comprising contacting an aqueoussolution containing at least two metals selected from molybdenum,cobalt, nickel, zinc and iron with an organic solvent and anoxime-containing reagent composition comprising an oxime having astructure represented by:

wherein R¹ is hydrogen or CH₃, R³ is a C8-12 alkyl group, R² and R⁴ arehydrogen, R⁵ is a methyl group, at a predetermined pH, the predeterminedpH selected to provide a high first metal extraction and a low secondmetal extraction; and separating the first metal from the solution.

According to one or more embodiments of this aspect, the oxime is aketoxime and has a structure represented by:

and the first and second metals are selected from the group consistingof nickel, molybdenum and cobalt.

In one or more further embodiments, the organic phase further comprisesan aldoxime having a structure represented by:

According to one or more embodiments, the ketoxime and aldoxime arepresent in a molar ratio of ketoxime to aldoxime ranging from about85:15 to about 25:75.

In one or more embodiments of this aspect, the oxime is an aldoxime andhas a structure represented by:

and the first and second metals are selected from the group consistingof zinc, nickel, molybdenum and cobalt.

In further embodiments, the organic phase further comprises a ketoximehaving a structure represented by:

According to one or more embodiments, the ketoxime and aldoxime arepresent in a molar ratio of ketoxime to aldoxime ranging from about85:15 to about 25:75.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of the level of copper in severalstripped organic solutions containing various ratios of 3-methylketoxime and 3-methyl aldoxime.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced orbeing carried out in various ways.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

The term “NSAO” as used herein is used interchangeably with5-nonylsalicylaldoxime, and refers to a compound having the structure:

The term “DSAO” as used herein is used interchangeably with5-dodecylsalicylaldoxime, and refers to a compound having the structure:

The term “HNAO” as used herein is used interchangeably with5-nonyl-2-hydroxyacetophenonoxime, and refers to a compound having thestructure:

The term “3-MNSAO” as used herein is used interchangeably with3-methyl-5-nonylsalicylaldoxime, and refers to a compound having thestructure:

The term “3-MHNAO” as used herein is used interchangeably with3-methyl-5-nonyl-2-hydroxyacetophenone oxime, and refers to a compoundhaving the structure:

The term “3-methyl oxime” as used herein refers to a compound having astructure represented by:

wherein R₅ is methyl; R₁ is hydrogen, a C₁₋₂₂ linear or branched alkylor alkenyl group, a C₆ aryl group or a C₇₋₂₂ aralkyl group; R²-R⁴ areeach independently hydrogen, halogen, a linear or branched C₆₋₁₂ alkylgroup, OR⁶ wherein R⁶ is a C₁₋₂₂ linear or branched alkyl group, a C₂₋₂₂linear or branched alkenyl group, a C₆ aryl group, or a C₇₋₂₂ aralkylgroup.

The term “3-methyl ketoxime” as used herein refers to a compound havinga structure represented by:

wherein R₅ is methyl; R₁ is a C₁₋₂₂ linear or branched alkyl or alkenylgroup, a C₆ aryl group or a C₇₋₂₂ aralkyl group; R²-R⁴ are eachindependently hydrogen, halogen, a linear or branched C₆₋₁₂ alkyl group,OR⁶ wherein R⁶ is a C₁₋₂₂ linear or branched alkyl group, a C₂₋₂₂ linearor branched alkenyl group, a C₆ aryl group, or a C₇₋₂₂ aralkyl group

The term “3-methyl aldoxime” as used herein refers to a compound havinga structure represented by:

wherein R₅ is methyl; R₁ is hydrogen; R²-R⁴ are each independentlyhydrogen, halogen, a linear or branched C₆₋₁₂ alkyl group, OR⁶ whereinR⁶ is a C₁₋₂₂ linear or branched alkyl group, a C₂₋₂₂ linear or branchedalkenyl group, a C₆ aryl group, or a C₇₋₂₂ aralkyl group.

Reagents

A first aspect of the invention relates to reagent compositions. In oneor more embodiments, the compositions comprise a mixture of at least twooximes, a ketoxime and an aldoxime. The ketoxime has a structurerepresented by Formula I:

wherein R₅ is a C₁₋₂₂ linear or branched alkyl group; R₁ is a C₁₋₂₂linear or branched alkyl or alkenyl group, a C₆ aryl group or a C₇₋₂₂aralkyl group; R²-R⁴ are each independently hydrogen, halogen, a linearor branched C₆₋₁₂ alkyl group, OR⁶ wherein R⁶ is a C₁₋₂₂ linear orbranched alkyl group, a C₂₋₂₂ linear or branched alkenyl group, a C₆aryl group, or a C₇₋₂₂ aralkyl group; and the aldoxime has a structurerepresented by Formula II:

wherein R₅ is a C₁₋₂₂ linear or branched alkyl group; R₁ is hydrogen;R²-R⁴ are each independently hydrogen, halogen, a linear or branchedC₆₋₁₂ alkyl group, OR⁶ wherein R⁶ is a C₁₋₂₂ linear or branched alkylgroup, a C₂₋₂₂ linear or branched alkenyl group, a C₆ aryl group, or aC₇₋₂₂ aralkyl group.

In one embodiment of the invention, the R³ is a C₈₋₁₂ linear or branchedalkyl group for Formula I and/or Formula II. In another embodiment, theR³ of Formula I and/or II is dodecyl. In yet other embodiment, the R³ ofFormula I and/or II is nonyl. In yet another embodiment, R⁵ is a C₁₋₃linear or branched alkyl or alkoxy group for the compound of Formula Iand/or II.

In one embodiment, the ketoxime (Formula I) and aldoxime (Formula II)reagents each have a methyl group substituted at the R⁵ position. Inanother embodiment, the ketoxime has a structure represented by FormulaIII:

wherein R¹ is hydrogen, halogen, a linear or branched C₆₋₁₂ alkyl groupand R² is a C₁₋₂₂ linear or branched alkyl or alkenyl group; and thealdoxime has a structure represented by Formula IV:

wherein R¹ is hydrogen, halogen, a linear or branched C₆₋₁₂ alkyl groupand R² is hydrogen.

In yet another embodiment, the ketoxime is a 3-methyl ketoxime having astructure represented by:

and the aldoxime is a 3-methyl aldoxime having a structure representedby:

In one or more embodiments where a ketoxime and aldoxime are used, theratio of ketoxime to aldoxime can be varied. In various embodiments, themolar amount of ketoxime can be about 25%, 30%, 40%, 50%, 60%, 65% 70%,75%, 80%, or 85% of the total amount of oxime. Thus, in a specificembodiment, the molar ratio of ketoxime to aldoxime is about 85%ketoxime to about 15% aldoxime. In another specific embodiment, themolar ratio of ketoxime to aldoxime is about 60% ketoxime to about 40%aldoxime. In yet another embodiment, the molar ratio of ketoxime toaldoxime ranges from about 85:15 to about 25:75, more specifically fromabout 80:20 to about 30:70, and even more specifically from about 80:20to about 40:60. Accordingly, in a very specific embodiment, the molarratio of 3-methyl ketoxime to 3-methyl aldoxime is about 85% ketoxime toabout 15% aldoxime. In another specific embodiment, the molar ratio of3-methyl ketoxime to 3-methyl aldoxime is about 60% ketoxime to about40% aldoxime.

Methods of making such individual reagent compounds are known in theart, such as those disclosed in U.S. Pat. No. 6,632,410, the entirecontents of which are incorporated herein by reference. For example,3-methyl-5-nonylsalicylaldoxime can be made by reacting o-cresol withtripropylene in the presence of an acid catalyst such as AMBERLYST® 15resin to form 4-nonyl-2-cresol which is in turn converted to thealdehyde by reaction with para-formaldehyde in the presence of acatalyst such as titanium cresylate. The 3-methyl-5-nonylsalicylaldehydeis then reacted with hydroxylamine sulfate to form the3-methyl-5-nonylsalicylaldoxime. In all cases, the total number ofcarbon atoms in all of R²-R⁵ groups must be great enough so that thecorresponding copper-extractant complex is soluble in the hydrocarbonsolvent.

The feedstock solution containing dissolved metal values is contactedwith the water-immiscible organic solution comprised of a hydrocarbonsolvent as described herein and one or more reagent compositions of theFormula I and/or Formula II for a period of time sufficient to allow theoxime described herein to form a complex with the iron and copper ions.The feedstock can be contacted by the organic solution in any mannerthat brings the two immiscible phases together for a period of timesufficient to allow the compounds of Formula I and/or Formula II to forma complex with the metal ions. This includes shaking the two phasestogether in a separatory funnel or mixing the two phases together in amix tank as described in U.S. Pat. No. 4,957,714, the entire contents ofwhich is incorporated herein by reference.

Reagent compositions according to one or more embodiments includemodifiers that can be added to the reagent to increase functionality.U.S. Pat. Nos. 4,978,788; 6,177,055; 6,231,784; 7,585,475 and 7,993,613,the contents of which are incorporated herein by reference, provideexamples of modifiers that can be used in accordance with embodiments ofthe present invention. For example, the use of highly branched chainaliphatic or aliphatic-aromatic C₁₀-C₃₀ esters or C₁₀-C₃₀ alcohols havebeneficial results as strip modifiers. Another example is an equilibriummodifier, where the modifier is a linear diester or polyester of anunbranched monocarboxylic acid or unbranched dicarboxylic acid and anunbranched alcohol. One embodiment of the invention is the reagentcomposition described above, further comprising thermodynamic modifiers.A second embodiment is the reagent composition described above, furthercomprising kinetic modifiers. Examples of suitable kinetic modifiersinclude, but are not limited to, dioximes such as 8,9-dioximohexadecaneor alpha-bromocarboxylic acids such as alpha-bromolauric acid. In aparticular embodiment, the kinetic modifier comprises5,8-diethyl-7-hydroxydodecan-6-oxime.

The reagent compositions in one or more embodiments include a solvent inwhich the reagent is dissolved. In one embodiment, the solvent comprisesa water immiscible organic solvent. In another embodiment, the waterimmiscible organic solvent is selected from the group consisting ofkerosene, benzene, toluene, xylene and combinations thereof.

The oximes in the composition can be present in any suitableconcentration for extraction. For example, in one or more embodiments,concentration of the oxime ranges from about 0.018M to about 1.1M. Inspecific embodiments, the concentration of oxime ranges from about0.018M to about 0.9M or 0.018M to about 0.72M. In embodiments in which aketoxime and aldoxime are present, the concentration of both ketoximeand aldoxime ranges from about 0.018M to about 0.9M or from about 0.018Mto about 0.72M. The reagent composition may also be concentrated.Concentrated forms can be useful, for example, for transporting thereagent composition. Several embodiments of concentrated forms can havean oxime concentration of about 1.7M or about 1.8M and up to about2.25M, 2.5M, and 2.6M. This oxime concentration can be the combinedconcentration of the oximes in embodiments where more than one oxime ispresent.

A second aspect of the invention relates to a reagent compositioncomprising a first oxime having a structure represented by:

wherein R⁵ is a C₁₋₂₂ linear or branched alkyl group; R¹ is a C₁₋₂₂linear or branched alkyl or alkenyl group, a C₆ aryl group or a C₇₋₂₂aralkyl group; R²-R⁴ are each independently hydrogen, halogen, a linearor branched C₆₋₁₂ alkyl group, OR⁶ wherein R⁶ is a C₁₋₂₂ linear orbranched alkyl group, a C₂₋₂₂ linear or branched alkenyl group, a C₆aryl group, or a C₇₋₂₂ aralkyl group; and5,8-diethyl-7-hydroxydodecan-6-oxime.

Processes for Metal Recovery

Another aspect of the invention relates to a method for the recovery ofa metal from a metal-containing aqueous solution, the method comprising:contacting the metal-containing aqueous solution with an organic phasecomprising a water immiscible solvent and a reagent compositioncomprising a mixture of a first oxime represented by formula I and asecond oxime represented by formula II to extract at least a portion ofthe metal values into the organic phase; separating the resultantmetal-pregnant organic phase from the resultant metal-barren aqueousphase; and recovering metal values from the metal-pregnant organicphase. In one embodiment, copper from a copper-containing aqueoussolution is recovered, which includes contacting the copper-containingaqueous solution with an organic phase comprising a water immisciblesolvent and a reagent composition of the type described herein. Anotherembodiment is where the recovered metal is selected from the groupconsisting of uranium, molybdenum, cobalt, copper, nickel andcombinations thereof. Other specific embodiments of such methods will bedescribed further herein.

In one embodiment, the ketoxime (Formula I) and aldoxime (Formula II)reagents each have a methyl group substituted at the R⁵ position. Inanother embodiment, the ketoxime has a structure represented by FormulaIII:

wherein R¹ is hydrogen, halogen, a linear or branched C₆₋₁₂ alkyl groupand R² is a C₁₋₂₂ linear or branched alkyl or alkenyl group; and thealdoxime has a structure represented by Formula IV:

wherein R¹ is hydrogen, halogen, a linear or branched C₆₋₁₂ alkyl groupand R² is hydrogen.

In yet another embodiment, the ketoxime is a 3-methyl ketoxime having astructure represented by:

and the aldoxime is a 3-methyl aldoxime having a structure representedby:

As will be appreciated in light of the above discussion of the resultsof the degradation testing, in one or more embodiments, the methodincludes 3-methyl reagents are used for extraction occurring over awider temperature range than is presently commercially feasible withexisting reagents. As discussed above, extraction of extremely richoxide ores, processes that result in the production of warmer leachsolutions and processes conducted in warmer climates require improvedreactant compositions capable of operating at higher temperatures thanis presently possible. In one embodiment, the metal recovered isselected from the group consisting of copper, uranium, molybdenum,nickel, zinc, cobalt and combinations thereof. In another embodiment,the metal recovered is copper.

In one or more embodiments, reagent compositions and processes forrecovering copper are provided that can be used in the range of about15° C. to about 60° C. In specific embodiments, reagent compositions andprocesses of copper extraction using such compositions can be performedat temperatures exceeding 30° C., 35° C., 40° C., 45° C., and 50° C. Inspecific embodiments, extraction can be carried out in the range ofabout 25° C. to about 60° C., of about 25° C. to about 50° C., of about35° C. to about 60° C., and of about 35° C. to about 50° C. Othervariants of ranges within the values discussed above are possible. Theoxime reagents described herein are advantageously used at highertemperatures, as currently used oximes undergo hydrolytic degradationand cause operational problems and increased cost.

In embodiments in which the recovery of copper is performed at anelevated temperature, the composition can include a ketoxime representedby the structure of formula I described above. In specific embodiments,the composition can comprise a mixture containing a ketoxime representedby the structure of formula I and an aldoxime represented by thestructure of formula II described above. In one or more embodiments, thecomposition can include a solvent and modifiers as described above.

According to one or more embodiments, a feature of one or more of thereagent compositions and/or methods described herein is that theyexhibit improved hydrolytic stability compared to currently used oximesfor extraction. While not wishing to be bound by theory, it is possiblethat a combination of effects leads to the added stability. For example,with 3-methyl aldoxime and 3-methyl ketoxime, it is believed that themethyl group ortho to the phenol changes the orientation of the oximefunctional group at the interface. This change in orientation sheltersthe oxime functional group from hydrolysis.

One advantage of one or more of the reagents and methods describedherein is resistance to nitration. Nitration of current reagents (DSAO,NSAO, and HNAO) is accomplished by electrophilic aromatic substitutionwhich is illustrated in Schematic 1. As the nitro oximes are extremelystrong copper chelators, they cannot be stripped under typical plantconditions resulting in a loss of net transfer. The oxime depicted inSchematic 1 can be used to represent any of the current reagents. Thenitration can only take place at the position ortho to the phenol due tothe resonance stabilization it affords the intermediate (2). This is awell known general reaction scheme in synthetic chemistry and has beeninvestigated thoroughly.

In the case of the new extractants, substitution at the position orthoto the phenol group prevents nitration. This renders these compoundsnitration resistant under the conditions found in typical miningsolutions. In one embodiment, 3-methyl ketoximes and 3-methyl aldoximes,(including, but not limited to, 3-MHNAO and 3-MNSAO) are used, such thatthe methyl group ortho to the phenol group prevents nitration.

Accordingly, yet another aspect of the invention pertains to a method ofextracting a metal from a nitrate-containing aqueous solution, themethod comprising: contacting a nitrate-containing aqueous solutioncontaining dissolved metal values with an organic phase comprising awater immiscible solvent and a reagent composition comprising an oximehaving a structure represented by:

wherein R¹ is hydrogen or CH₃, R³ is a C8-12 alkyl group, R² and R⁴ arehydrogen, R⁵ is a methyl group, to extract at least a portion of themetal values into the organic phase to provide a metal-pregnant organicphase and a metal-barren aqueous phase; separating the resultantmetal-pregnant organic phase from the metal-barren aqueous phase; andrecovering metal values from the metal-pregnant organic phase. Inspecific embodiments, R⁵ is a methyl or methoxy group, and in morespecific embodiments, the oxime is

or mixtures thereof.

The metal according to such processes containing nitrate can include,but are not limited to, the metals selected from the group consisting ofcopper, molybdenum, uranium, rare earth metals (scandium, yttrium,lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, and lutetium) and combinations thereof. In a specificembodiment, the metal is copper. In one embodiment, thenitrate-containing aqueous solution has a concentration of nitrate thatranges from about 1 grams per liter to about 50 grams per liter, andmore specifically 3 grams per liter to about 35 grams per liter. Inspecific embodiments, the nitrate-containing aqueous solution alsocontains chloride, wherein the chloride has a concentration ranging fromabout 1 gram per liter to about 30 grams per liter. In one or moreembodiments, the pH of the nitrate-containing aqueous solution rangesfrom about 0.6 to about 2.0.

Such methods of extracting a metal from a nitrate-containing aqueoussolution may also have applicability in proposed leaching schemes suchas those described in U.S. Pat. No. 6,569,391, where sodium nitrate isadded to a dilute sulfuric acid solution to leach copper sulfides. U.S.Pat. No. 6,569,391 is herein incorporated by reference in its entirety.

3-methyl aldoximes, 3-methyl ketoximes and their blends transfer muchlower quantities of iron than HNAO. The transfer of iron is verydependent on the conditions used in the static test. However, HNAOtransfers between 2-10 times more iron than the analogous 3-methylspecies. In most cases, the iron values are so low that they are at thelimits of detection. The excellent results of the iron/copperselectivity are demonstrated in Example 2 below.

In one or more embodiments where a ketoxime and aldoxime are used, theratio of ketoxime to aldoxime can be varied. In various embodiments, themolar amount of ketoxime can be about 25%, 30%, 40%, 50%, 60%, 65% 70%,75%, 80%, or 85% of the total amount of oxime. Thus, in a specificembodiment, the molar ratio of ketoxime to aldoxime is about 85%ketoxime to about 15% aldoxime. In another specific embodiment, themolar ratio of ketoxime to aldoxime is about 60% ketoxime to about 40%aldoxime. In yet another embodiment, the molar ratio of ketoxime toaldoxime ranges from about 85:15 to about 25:75, more specifically fromabout 80:20 to about 30:70, and even more specifically from about 80:20to about 40:60. Accordingly, in a very specific embodiment, the molarratio of 3-methyl ketoxime to 3-methyl aldoxime is about 85% ketoxime toabout 15% aldoxime. In another specific embodiment, the molar ratio of3-methyl ketoxime to 3-methyl aldoxime is about 60% ketoxime to about40% aldoxime.

One or more of the reagent compositions and methods described herein mayalso be used for extraction from ammoniacal solutions. In particular,these may be used to extract nickel, cobalt and/or zinc from ammoniacalsolutions. For example, nickel can be extracted from ammoniacalsolutions using HNAO. Depending on the nickel ammonia complex, thereaction proceeds using either Scheme 2 or Scheme 3.

Cobalt is often found in conjunction with nickel. It is advantageous toconvert Co⁺² to Co⁺³ by oxidation, because nickel is extractedselectivity over Co⁺³ by ketoximes. Considering that data suggests thatcobalt-loading can lead to faster degradation of the ketoxime, the addedstability and possible lower cobalt loading of the 3-methyl ketoxime(including, but not limited to, 3-MHNAO) would be advantageous fornickel extraction.

Therefore, another aspect of the invention pertains to methods ofextracting metal from aqueous ammoniacal solutions containing metalvalues comprising: contacting an ammoniacal solution containing metalvalues with an organic solution comprising a water immiscible organicsolvent containing dissolved extractant comprising an oxime having astructure represented by:

wherein R¹ is hydrogen or CH₃, R³ is a C8-12 alkyl group, R² and R⁴ arehydrogen, R⁵ is a methyl group, forming a water immiscible organicphase, whereby metal values are extracted from the aqueous ammoniacalsolution into the organic phase, thereby providing a metal-pregnantorganic phase and a metal barren aqueous phase; separating themetal-barren aqueous phase from the metal-pregnant organic phase; andrecovering the metal values from the metal-pregnant organic phase. Inone or more embodiments, the metal is selected from one or more ofnickel, zinc and copper. In other embodiments, R³ is octyl, nonyl ordodecyl.

In specific embodiments, the oxime can have a structure represented by:

or mixtures thereof.

The addition of ammonia antagonists such as those described in U.S. Pat.No. 6,210,647, the contents of which are herein incorporated byreference, would also be expected to result in further reductions inammonia loading when combined with the 3-MNSAO or 3-MHNAO or blendsthereof. Such ammonia antagonists are referred to as “non-hydrogen bonddonating” and are only “hydrogen bond accepting” compounds. The ammoniaantagonists for use in the present improvement are those organichydrogen bond acceptor compounds containing one or more of the followingorganic functionalities: ester, ketone, sulfoxide, sulfone, ether, amineoxide, tertiary amide, phosphate, carbonate, carbamate, urea, phosphineoxide, and nitrile and having greater than 8 carbon atoms, up to about36 carbon atoms and a water solubility of less than 100 ppm, moredesirably less than 50 ppm and preferably less than 20 ppm. In aspecific embodiment, the ammonia antagonist comprises2,2,4-trimethylpentane-1,3-diol diisobutyrate. Other illustrativeammonia antagonists which are only hydrogen bond acceptor compounds are:alkyl esters and dialkyl ketones in which the alkyl groups contain from4 to about 12 carbon atoms, such as isobutyl isooctanoate and isobutylheptyl ketone and the dinitrile of dimerized fatty acids such asdimerized C18 fatty acids, (Dimer Acid™ dinitrile).

In yet another aspect, the invention pertains to methods of recoveringmetal from an aqueous solution, comprising: contacting an aqueoussolution containing at least two metals selected from molybdenum,cobalt, nickel, zinc and iron with an organic solvent and anoxime-containing reagent composition comprising an oxime having astructure represented by

wherein R¹ is hydrogen or CH₃, R³ is a C8-12 alkyl group, R² and R⁴ arehydrogen, R⁵ is a methyl group, at a predetermined pH, the predeterminedpH selected to provide a high first metal extraction and a low secondmetal extraction; and separating the first metal from the solution. Inspecific embodiments, R³ is nonyl. In other specific embodiments, theoxime used can be

or mixtures thereof. The metals can be zinc, nickel, molybdenum andcobalt.

According to one or more embodiments, the oxime compositions exhibit oneor more useful features including one or more of hydrolytic stability,good selectivity, fast kinetics and resistance to nitration. Thefollowing non-limiting examples are intended to demonstrate one or moreof these features.

EXAMPLES Example 1

Solutions (0.175 M) of 3-methyl-5-nonyl ketoxime and 3-methyl-5-nonylaldoxime in Conosol® 170ES, a typical hydrocarbon diluent from ConocoPhillips®, for solvent extraction applications, were prepared. Thesesolutions were then blended in the following proportions(ketoxime:aldoxime): 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 25:75 and0:100. Each solution was then contacted with a synthetic leanelectrolyte containing 35 gpl of copper as copper sulfate and 160 gpl ofsulfuric acid in deionized water by shaking for 3 minutes at an organicto aqueous ratio of 1. The phases were separated after shaking and theprocess was repeated for a total of 4 contacts. The equilibrated organicphase was then filtered through phase separation paper to removeresidual entrainment and analyzed for copper content by atomicabsorption spectroscopy. The results are summarized in FIG. 1.

As discussed above, the known mixtures of ketoxime with aldoxime have acopper content in the stripped organic that is lower than one wouldexpect based on consideration of the stripping behavior of theindividual oximes. In contrast, the results of Example 1 and FIG. 1demonstrate that the 3-methyl-ketoxime and 3-methyl-aldoxime blend doesnot behave in this way. The level of copper in the stripped organicscontaining various ratios of 3-methyl-ketoxime to 3-methyl-aldoxime veryclosely approximate a straight line, corresponding to what would beexpected theoretically. A very slight downward bow in FIG. 1 is withinthe experimental error of the method.

Example 2A

Organic solutions were prepared by dissolving LIX® 860N-I, LIX® 664N-LVand LIX®8180 in Conosol® 170ES at approximately 10% v/v so that theresultant solutions contained about 0.175 M standard aldoxime orketoxime. LIX® 860N-I is a solution of 5-nonylsalicylaldoxime inShellsol® D70, a hydrocarbon diluent from Shell Chemical. LIX® 664N-LVis a solution of 5-nonylsalicylaldoxime and di-n-butyladipate (0.8 M) inShellsol D70. LIX® 8180 is a solution of 2-hydroxy-5-nonylacetophenoneoxime in Shellsol D70. Solutions of 3-methyl-5-nonylsalicylaldoxime and3-MHNAO (3-MHNAO) (0.175 M) in Conosol® 170ES were also prepared. Aseries of blends were also prepared by mixing the above solutions togive a 50:50 blend on a volume basis of the LIX® 860N-I solution, theLIX® 664N-LV and LIX® 8180 with the 3-MHNAO solution. The resultantsolutions were then carried through the Standard Cognis Quality ControlTest for LIX® Oxime Reagents with the following modifications. Thestandard 1 liter glass beaker was replaced with a jacketed beaker sothat the temperature could be controlled precisely at 25° C. Samples ofthe emulsion were removed at 30, 60, 90, and 300 seconds. The 300 secondpoint was defined as 100% of equilibrium. The organic samples wereanalyzed for copper and iron content by atomic absorption spectroscopy.The results are summarized in Tables 1, 2 and 3.

TABLE 1 Comparison of Extraction Kinetics at 25° C. % of Equilibrium %of Equilibrium Sample @ 30 sec @ 60 sec 3-MHNAO 63 75 3-MNSAO 100   99.7 LIX ® 860N-I 98% 99% LIX ® 664N-LV 98% 98% LIX ® 8180 92% 98%LIX ® 860N-I:3-MHNAO 84 91 LIX ® 664N-LV:3-MHNAO 80 87 LIX ®8180:3-MHNAO 79 88 47:53 3-MNSAO:3-MHNAO 96 99

TABLE 2 Comparison of Strip Kinetics at 25° C. % of Equilibrium % ofEquilibrium Sample @ 30 sec @ 60 sec 3-MHNAO 50 81 3-MNSAO 100  100 LIX ® 860N-I 99% 100% LIX ® 664N-LV 100%  100% LIX ® 8180 80% 100% LIX ®860N-I:3-MHNAO 78 87 LIX ® 664N-LV:3-MHNAO 77 87 LIX ® 8180:3-MHNAO 3653 47:53 3-MNSAO:3-MHNAO 93 99

TABLE 3 Organic Copper to Iron ratio at 60 seconds at 25° C. Cu/FeSelectivity at Sample 60 Sec [Cu]/[Fe] 3-MHNAO 2215 3-MNSAO 18397 LIX ®860N-I 2987 LIX ® 664N-LV 4573 LIX ® 8180 2970 LIX ® 860N-I:3-MHNAO 2558LIX ® 664N-LV:3-MHNAO 1854 LIX ® 8180:3-MHNAO 2741 47:53 3-MNSAO:3-MHNAO51470

The overall results are surprising. Mixing the 3-MHNAO with LIX® 860N-I,LIX® 664N-LV, and LIX® 8180 result in products with slow/marginalkinetics in extraction and stripping. Surprisingly, the benefit of thefaster kinetics of the LIX® 860N-I, LIX® 664N-LV or LIX® 8180 is notobserved when any of them is mixed with the 3-MHNAO. Mixing the 3-MHNAOwith 3-MNSAO results in a mixture having excellent extraction andstripping kinetics as well as outstanding Cu/Fe selectivity.

Example 3

Solutions of 3-MNSAO and 3-MHNAO (0.175 M) in Conosol® 170ES wereprepared. A series of blends were also prepared by mixing the twosolutions at different volume ratios to give 3-MNSAO:3-MHNAO of 0:100,23:77, 29:71, 36:64, 42:58, 47:52, 60:40 and 100:0. These solutions werethen evaluated under conditions of the Standard Cognis Quality ControlTest for LIX® Oxime Reagents at 25° C. under the same condition asdescribed in Example 2A. The extraction kinetics and strip kinetics at60 sec., Cu/Fe selectivity and Net Cu Transfer were determined for eachmixture. The results are summarized in Table 7.

TABLE 7 Summary of Kinetics, Cu/Fe Selectivity and Net Cu Transfer atDifferent 3-MNSAO:3-MHNAO ratios Solution (3- Extraction Strip NetMNSAO:3- Kinetics % Kinetics % Cu/Fe Transfer MHNAO) @ 60 Sec @ 60 SecSelectivity gpl Cu  0:100 75 81 2215 3.90 23:77 82 94 4010 3.56 29:71 96100 47420 3.45 36:64 100 100 49130 3.31 42:58 100 100 24785 3.10 47:53100 99 51570 3.00 60:40 100 100 16920 2.64 100:0  100 100 18397 1.51

Based on the data in Table 7, the extraction kinetics are marginal at25° C. for the 23:77 blend, while net transfer is quite high. For the60:40 blend, the extraction and strip kinetics are excellent, but thenet transfer begins to fall off.

Example 4

The hydrolytic stability of the 5-nonylsalicylaldoxime (NSAO),5-dodecylsalicylaldoxime (DSAO), 2-hydroxy-5-nonylacetophenone oxime(HNAO), 3-MHNAO and 3-MNSAO were determined by preparing solutions ofthe reagents (about 0.175 M) in Shellsol® D70. These solutions were thencontacted with an aqueous solution containing 30 gpl of copper as coppersulfate and 180 gpl sulfuric acid in deionized water. The solutions werestirred in a 3 neck round bottom flask fitted with a condenser, paddlestirrer, and a thermometer. The condenser was fitted with a polyurethanefoam plug to minimize evaporation. The flask was immersed in an oil bathheated to 45° C. to maintain constant temperature. The aqueous wasperiodically replaced, initially on a weekly basis and finally on amonthly basis. Samples were periodically removed at weekly intervalsduring the first month, and then monthly thereafter. The samples weremax loaded with copper under the conditions of the Standard CognisQuality Control Test for LIX® Oxime Reagents at 25° C. The residualoxime content was calculated based on the copper max load valuesassuming a complex consisting of two oximes per copper. The results wereplotted against time and a point at which half the oxime remained wasdetermined by extrapolation. This was termed the half life of the oxime.The results are summarized in Table 8.

TABLE 8 Summary of Reagent Half Lives Reagents Half Life (Days) NSAO 90DSAO 167 HNAO 325 3-MHNAO 2100 3-MNSAO 725

3-MNSAO is approximately 7 times more hydrolytically stable than NSAOand 3-MHNAO is 6.5 times more hydrolytically stable than HNAO.

Example 5

Solutions of 3-methyl aldoxime, 3-methyl-ketoxime and a blend using28.8% 3-methyl aldoxime and 71.2% 3-methyl-ketoxime were made up suchthat they were roughly 0.11M total oxime in Conosol® 170ES diluent.Solutions of various metals were made up approximately 0.05M in DI waterand the pH adjusted to a pH of 1.0 with dilute sulfuric acid.Individually each organic was contacted in a baffled beaker using amagnetic stir bar for agitation at an O:A of 1:1 with an aqueoussolution containing one metal. A pH probe was used to monitor the pH ofthe aqueous continuous emulsion. Once the pH was stable indicating thatthe system was at equilibrium, a sample of emulsion was drawn, thephases were allowed to separate and samples of the organic and aqueousphases were saved separately for analysis by atomic absorptionspectroscopy. Once a sample was drawn the pH was increased by adding aportion of an aqueous ammonium hydroxide solution, the mixture wasallowed to equilibrate and another emulsion sample was drawn and labeledwith the pH for organic and aqueous analysis. The pH was adjusted slowlydrawing samples at intervals up to a pH of 7. The results are reportedbelow in Table 9 with percentage of metal extracted by the reagent withrespect to pH for each metal and reagent.

TABLE 9 Metal extraction over a pH range for various reagent blends pH 12 3 4 5 6 7 28.8% 3-MNSAO and 71.2% 3-MHNAO Percent Metal Cu 45%  90% 100%  100%  100%  100%  100% Extracted Fe 0% 5% from Aqueous Ni 0% 0% 0%50% 80% 95%  95% Co 0% 0% 0%  0%  5% 20%  70% 3-MNSAO Percent Metal Cu85%  95%  100%  100%  100%  100%  100% Extracted Fe 0% 30%  from AqueousNi 0% 0% 0% 90% Co 0% 0% 0%  0% 40% 95% 100% Mo 65%  70%  70%  3-MHNAOPercent Metal Cu 50%  90%  100%  100%  100%  100%  100% Extracted Fe 0%5% from Aqueous Ni 0% 0% 0% 40% 85% 90%  95% Co 0% 0% 0%  0%  5% 45% Mo65%  65%  65%  35% 30%

Example 6

Solutions (0.52 M) of LIX®8180, methyl aldoxime (3-MNSAO) and methylketoxime (3-MHNAO) in Conosol® 170ES, a typical hydrocarbon diluent fromConoco Phillips for solvent extraction applications, were prepared. Theorganics were tested using the Blue Line Technical Bulletin CognisQuality Control Test For LIX® Nickel Oxime Reagents. The extraction andammonia loading portion of this experiment was repeated for the LIX®8180and 3-MHNAO replacing the Standard Nickel Extraction Aqueous Phase witha solution that contains 15±0.1 g/l Cu₊₂ (as sulfate), 32.5 g/l NH₃ and25 g/l (NH₄)2SO4 drawing samples at 30, 60, 90 and 300 seconds.Extraction of the metals from ammonia aqueous solutions, the extractionof ammonia from loaded organic and the stripping of nickel wererecorded. Molarity of ammonia loaded on the organic phase is reportedafter filtering to remove the entrained aqueous, results of extractionare reported as percentage extracted from the aqueous extractionsolution, results of stripping are reported as the percentage of metalremoved from the loaded organic. The results are summarized in Table 10.

TABLE 10 Nickel and Copper Nickel Test Copper Test LIX ®8180 3-MNSAO3-MHNAO LIX ®8180 3-MHNAO E30 93.93% 78.33% 64.80% E30 94.73% 96.07%E300 94.60% 94.33% 90.40% E60 94.40% 95.80% S10 (600 sec) 99.42% 15.83%27.43% E90 94.67% 95.93% S20 (1200 sec) 99.92% 35.12% 53.17% E300 94.47%96.07% Ammonia loading M of NH3 0.00804 0.00274 0.00355 M of NH3 0.009470.00235

It can be seen from the results above that 3-MNSAO and 3-MHNAO loadsignificantly less ammonia than LIX® 8180 which is based on the standardketoxime which is currently the reagent of choice for extraction ofnickel and copper from ammonia.

Example 7

Solutions of 3-methyl-ketoxime and a blend consisting of 28.8% 3-methylaldoxime and 71.2% 3-methyl-ketoxime were made up such that they wereroughly 0.175 M oxime in Conosol® 170ES diluent. Both solutions werefurther spiked to give concentrations of 0.0028M, 0.014M, or 0.028M5,8-diethyl-7-hydroxydodecan-6-oxime (LIX® 63 Oxime) and a blank to givea total of eight solutions. These were contacted with a syntheticaqueous PLS (6 g/L Cu, 3 g/L Fe with a pH of 2 in DI water) followingthe standard QC test with some modifications, it was scaled down to 100ml of each solution in a 250 ml baffled jacketed beaker at 25° C.Kinetic samples were drawn at 30, 60, 90, and 300 sec and saved forcopper analysis by atomic absorption spectroscopy. The remaining organicfrom the previous step was contacted at an O:A 1:1 with a syntheticelectrolyte aqueous solution (35 g/L Cu and 160 g/L free sulfuric acidin DI water). Kinetic samples were drawn at 30, 60, 90, and 300 sec andsaved for copper analysis by atomic absorption spectroscopy. The kineticdata is summarized in Table 11.

TABLE 11 Summary of metallurgical data for LIX ®63 copper experimentPercent copper Percent copper Iron extraction stripped loaded Cu @ Cu @Cu @ Cu @ E30 30 sec 60 sec 30 sec 60 sec Cu/Fe 3MHNAO 46.0% 59.6% 24.6%31.1% 589 3MHNAO & 0.0028M 48.2% 63.3% 33.8% 37.8% 1558 LIX ® 63 Oxime3MHNAO & 0.014M 61.8% 79.4% 29.4% 34.0% 2191 LIX ®63 Oxime 3MHNAO &0.028M 69.7% 81.9% 18.2% 25.1% 1814 LIX ®63 Oxime 3M Blend 64.8% 75.6%52.2% 64.6% 633 3M Blend & 0.0028M 65.1% 81.1% 42.6% 48.1% 1479 LIX ®63Oxime 3M Blend & 0.014M 70.4% 79.9% 42.5% 50.3% 1343 LIX ®63 Oxime 3MBlend & 0.028M 77.9% 88.3% 44.2% 58.3% 1525 LIX ®63 Oxime

Addition of the 5,8-diethyl-7-hydroxydodecan-6-oxime resulted in fasterextraction kinetics with no significant improvement in strippingkinetics.

Example 8

Solutions containing 3-methyl aldoxime, 3-methyl ketoxime and a blendconsisting of 28.8% 3-methyl aldoxime and 71.2% 3-methyl ketoxime weremade up such that they were roughly 0.175 M in total oxime and containedeither 0.0007 or 0.0149 M of a thermodynamic modifier. The hydrocarbondiluent was Conosol® 170ES diluent. The thermodynamic modifiers weredi-n-butyl adipate (DBA), iso-tridecanol (TDA) and2,2,4-trimethyl-1,3-pentanediol di-isobutyrate (TXIB). These solutionswere then contacted with a synthetic aqueous PLS (6 g/L Cu, 3 g/L Fewith a pH of 2 in DI water) to demonstrate loading of the metal and thencontacted with a synthetic electrolyte aqueous solution (35 g/L Cu and160 g/L free sulfuric acid in DI water) to remove the metal. Thesecontacts were done at an O:A of 2:1 for extraction 20 ml to 10 ml and1:1 for stripping 10 ml to 10 ml on an autoshaker with 30 ml separatoryfunnels. The loaded and stripped organic samples were analyzed forcopper and iron by atomic absorption spectrometry. The copper and ironvalues of the resultant solutions of each contact are reported in Table12.

TABLE 12 Thermodynamic Modifier Blend Data 3-MNSAO 3-MHNAO Blend of3-MNSAO and 3-MHNAO Loaded Stripped Loaded Loaded Stripped Loaded LoadedStripped Loaded Thermo- Organic Organic Organic Organic Organic OrganicOrganic Organic Organic dynamic Copper Copper Iron Copper Copper IronCopper Copper Iron Modifier (gpl) (gpl) (gpl) (gpl) (gpl) (gpl) (gpl)(gpl) (gpl) DBA .0007 2.776 3.182 0.0074 0.975 0.535 0.0048 1.875 1.0860.0042 DBA .0149 2.393 1.728 0.0032 0.707 0.304 0.0033 1.364 0.4930.0031 TDA .0007 2.886 3.199 0.0071 0.96 0.387 0.005 1.934 1.078 0.0042TDA .0131 2.604 1.857 0.0027 0.752 0.168 0.0039 1.579 0.498 0.0033 TXIB.0008 2.896 3.359 0.0082 0.91 0.517 0.005 1.593 1.159 0.006 TXIB .01692.492 2.137 0.0045 0.774 0.346 0.004 1.269 0.628 0.0049 No 2.919 3.6940.0103 1.003 0.572 0.0055 1.854 1.306 0.006 additive No 2.925 3.6940.0105 0.961 0.526 0.0053 1.873 1.333 0.006 additive

The data indicates that addition of thermodynamic modifiers can be usedto adjust the stripping behavior of these reagents.

Example 9

The Cognis Quality Control Test for LIX® Nickel Oxime Reagents wasmodified to reduce the volume of organic solution required. The testinvolves extraction of nickel from an ammoniacal solution followed bystripping with a sulfuric acid solution. Three organic solutions wereprepared to contain 0.5M 3-methyl aldoxime and varying levels (0.0028M,0.028M, and 0.14M) of 5,8-diethyl-7-hydroxydodecan-6-oxime (LIX®63Oxime) in Conosol® 170 ES diluent. The starting organic volume wasscaled down to 100 ml and all other volumes scaled down proportionally.The mixing took place in a 250 ml baffled jacked beaker with a 3.175 cmdiameter QC impellor at 1750 RPM. Samples were drawn for extraction at30, 60, 90, and 300 seconds and for strip at 1, 5, 10, and 20 min. Thepercent of stripping was calculated as the difference between the nickelconcentration at 300 sec of extraction and the nickel concentration at agiven stripping time divided by the nickel concentration at 300 sec ofextraction times 100. All other experimental parameters were held thesame as the standard procedure. The results are summarized in Table 13.

TABLE 13 Effect of 5,8-diethyl-7-hydroxydodecan-6-oxime concentration onkinetics of extraction of nickel from ammonia and stripping of nickelwith acid from 3-methyl aldoxime 0.0028M LIX ®63 Oxime 0.028M LIX ®63Oxime 0.14M LIX ®63 Oxime g/L Ni % of final g/L Ni % of final g/L Ni %of final Extraction 30 2.11 87.63% 1.65 84.46% 2.05 89.32% (sec) 60 3.0894.65% 2.96 93.97% 3.22 98.01% 90 3.54 97.93% 3.56 98.26% 3.45 99.73%300 3.82 100.00% 3.80 100.00% 3.49 100.00% Strip 1 3.26 4.08% 2.93 6.30%1.25 16.58% (min) 5 2.41 10.23% 0.64 22.91% 8.07 40.21% 10 1.94 13.64%7.97 42.20% 4.92 63.56% 20 0.60 23.33% 5.57 59.61% 1.53 88.63%

The addition of 5,8-diethyl-7-hydroxydodecan-6-oxime does not have anappreciable effect of the kinetics of extraction of nickel fromammoniacal solutions by 3-methyl aldoxime. Extraction from ammoniacalsolutions is typically very fast in any case and any incremental changeswould be hard to detect. In the case of stripping, however; addition ofthe 5,8-diethyl-7-hydroxydodecan-6-oxime significantly improvesstripping kinetics.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present invention without departing from the spirit andscope of the invention. Thus, it is intended that the present inventioninclude modifications and variations that are within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of recovering metal from an aqueoussolution, the method comprising: contacting an aqueous solutioncontaining at least two metals selected from molybdenum, cobalt, nickel,zinc and iron with an organic solvent and an oxime-containing reagentcomposition comprising an oxime having a structure represented by:

wherein R¹ is hydrogen or CH₃, R³ is a C8-12 alkyl group, R² and R⁴ arehydrogen, R⁵ is a methyl group, at a predetermined pH, the predeterminedpH selected to provide a high first metal extraction and a low secondmetal extraction; and separating the first metal from the solution. 2.The method of claim 1, wherein the oxime is a ketoxime and has astructure represented by:

and the first and second metals are selected from the group consistingof nickel, molybdenum and cobalt.
 3. The method of claim 2, wherein theorganic phase further comprises an aldoxime having a structurerepresented by:


4. The method of claim 1, wherein the oxime is an aldoxime and has astructure represented by:

and the first and second metals are selected from the group consistingof zinc, nickel, molybdenum and cobalt.
 5. The method of claim 4,wherein the organic phase further comprises a ketoxime having astructure represented by:


6. The method of claim 5 wherein the ketoxime and aldoxime are presentin a molar ratio of ketoxime to aldoxime ranging from about 85:15 toabout 25:75.
 7. The method of claim 6, wherein the ketoxime and aldoximeare present in a molar ratio of ketoxime to aldoxime is about 70:30. 8.The method of claim 3 wherein the ketoxime and aldoxime are present in amolar ratio of ketoxime to aldoxime ranging from about 85:15 to about25:75.
 9. The method of claim 8, wherein the ketoxime and aldoxime arepresent in a molar ratio of ketoxime to aldoxime is about 70:30.
 10. Themethod of claim 1, wherein the predetermined pH ranges from 1 to
 7. 11.The method of claim 1, wherein the pH is adjusted using sulfuric acid oraqueous ammonium hydroxide solution.